The ion implantation of silicon with boron ions to create an area of positive charge is commonplace in the semiconductor industry. It is recognized that boron will rapidly migrate from silicon to the adjacent surface of silicon dioxide and subsequently diffuse into the silicon dioxide. In certain design situations, i.e. where the silicon to be doped with boron by ion implantation overlies an isolation dielectric layer of silicon dioxide, this seeming affinity of a boron ion implant for silicon dioxide can be a decided disadvantage. If the silicon structure is doped with a relatively large dose of boron ions, the boron will rapidly diffuse into the oxide layer upon heating to render the implant substitutional and, from there, will diffuse into adjacent surfaces, for example, into an underlying single crystalline silicon substrate. This substantial movement of boron ions into the isolation dielectric layer and, to a lesser degree, into the substrate can be very detrimental to the operation of any device incorporating it. A solution to this problem is provided in accordance with this invention.